Semiconductor wafers have become larger in scale, now with fabrication facilities commonly utilizing 300 mm wafers to be manufactured into semiconductor devices such as integrated circuits. The integrated circuits themselves have become larger in size with increasing circuit densities. As a consequence, the size of particulate contaminants that can destroy a circuit have decreased significantly, and strict particulate control is necessary during all phases of manufacturing, processing, transporting, and storage of semiconductor wafers.
In order to inhibit contamination by particulates during storage, processing, and handling operations, wafers are commonly stored and transported in sealed front-opening wafer containers that have a door secured by latches on the open front. The door can be typically removed manually or robotically. Such wafer containers are known in the industry as FOUPs, which is an acronym for front-opening unified pod, and FOSBs, an acronym for front-opening shipping box. Examples of such containers are generally disclosed in U.S. Pat. Nos. 6,644,477; 6,267,245; 6,216,874; 6,206,196; 6,010,008; and 5,944,194, all of which are commonly owned by the owners of the present invention and which are hereby fully incorporated herein by reference.
The doors on these types of containers are operated with robotic interfaces that have precisely positioned keys that insert into the front of the door to operate latching mechanisms to remove and place the door with respect to the container portion.
Semiconductor wafers are typically very thin and brittle. As a consequence, it is highly desirable wafers are firmly restrained in the container to inhibit movement. Further, the wafers should be cushioned against shocks that may cause breakage of the wafer.
Prior art containers typically have one or more wafer cushioning support or restraint structures fixed in the enclosure. These fixed structures may be supplemented by one or more wafer cushions fixed on the door, which provide support to the wafers when the door is engaged with the container. Most commonly, two fixed supports are spaced apart in the enclosure and one support is provided on the door so that wafers are supported at three roughly evenly spaced-apart locations.
While prior containers are generally satisfactory for most uses, it is desirable in some cases, particularly in wafer containers for single wafers, to provide additional support along the edge of the wafer facing the door to alleviate unsatisfactory deflection and movement of the wafer. What is needed in the industry is an alternative wafer cushioning means that enables firm support and cushioning along the front edge of a wafer.